Toothbrush

ABSTRACT

To provide a toothbrush that can easily and surely brush, particularly, lateral sides of molars and premolars and rear surfaces of incisors. A toothbrush comprising a rod-like block handle and a bristle section having a bristle tuft unit composed with a plurality of bristle tufts and extended to the end part of the block handle, wherein the bristle tuft unit is equipped with a head-end bristle tuft unit disposed in the head end section and a level difference unit provided on the block handle side rather than on the head-end bristle tuft unit, having still shorter bristle tufts and at the same time, formed throughout a plane range larger than the head-end bristle tuft unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to toothbrushes and particularly to a toothbrush for easily brushing molars, premolars, and incisors.

2. Description of the Related Art

As illustrated in FIG. 10, in general, a toothbrush 50 has a rod-like block handle 51 and a bristle section 55 having a bristle tuft unit 54 composed with a plurality of bristle tufts 53 disposed of, extended to the end part of the block handle 51 via a block head 52 and extended to the end part of the block handle 51.

Heretofore, in this kind of a conventional toothbrush 50, the bristle tuft unit 54 is formed in a rectangle shape on a flat surface way, and bristles have the same length from the top end portion to the rear end portion. The head end face portion 57 of the bristle tuft unit 54 is, therefore, formed flat.

In this way, in the toothbrush 50 with the same bristle length size of the bristle bundle unit 51 and the head end face portion 57 formed flat, it is empirically understood that nonconformities as described below would occur.

First, when teeth were brushed by the use of this kind of the conventional toothbrush 50, it was extremely difficult to brush, particularly, second premolars, first molars, and second molars which were located in the back of the oral cavity.

That is, as shown in FIG. 11, for example, in the event that a toothbrush 50 was inserted into an oral cavity 66 and an attempt was made to brush the second molar 56 with the head end face portion 57 of the bristle tuft unit 54 brought in contact with the top surface 75 of the second molar 56 in order to brush the top surface 57 of the second molar 56 and the gum-side lateral side 63 that faced the gum 68, the center portion 65 of the head end face portion 57 of the bristle tuft unit 45 came in contact with a protruded portion 64 because the protruded portion 64 was formed in four corners of the top surface 75 of the second molar 56.

As a result, the protruded portion 64 posed an impediment, the bristle tuft unit 54 was unable to go along the profile of the top surface 75 of the second molar 56 and the gum-side lateral side 63, and the bristle tuft 53 was prevented from going round up to the gum-side lateral side 63 of molar 56 and frequently was unable to thoroughly brush the gum-side lateral side 63.

In addition, second, as illustrated in FIG. 12, there was a trouble in that by toothbrushes 50, it was extremely difficult to brush lateral sides of the second molars 56, first molars 60, and second premolars 61 when an attempt was made to brush lateral sides of the second molars 56, first molars 60, and second premolars 61.

That is, between the second molar 56, first molar 60, and second premolar 61, planarly substantially V-letter shape clearances 59, 59 were formed and the flat head end face portion 57 of the bristle tuft unit 54 did not fit to profiles of lateral sides 56 a, 60 a, 60 b, and 61 a, which were disposed with acute angles formed each other, of the neighboring second molar 56 and first molar 60, or first molar 60 and second premolar 61, respectively.

As a result, since the bristle tuft 53 did not get into the inward of each of clearances 59 and 59, lateral sides 56 a, 60 a, 60 b, and 61 c of the second molar 56, first molar 60, and second premolar 61 were frequently unable to be thoroughly brushed.

Third, as shown in FIG. 13, there was a trouble in that using a conventional toothbrush 50, the tooth root 72 of the rear side 70 of the incisor 69, anterior tooth, was difficult to be brushed.

That is, the incisor 69 had a thick wall part 71 formed in the upper portion of the gum 68 and at the same time had the tooth root 72 formed still thinner, and had a raised portion 73 formed in the gum 68 in such a manner that the raised portion 73 surrounded the tooth root 72.

Consequently, in the event that the bristle tuft unit 54 was brought in contact with the rear side 70 of the incisor 69 in the longitudinal direction using the toothbrush 50 longitudinally in order to brush the rear side 70 of the incisor 69, the bristle tuft unit 54 of the conventional toothbrush 50 was blocked by the raised portion 73 and the thick wall part 71 and the bristle tuft unit 54 of the toothbrush 50 found it difficult to get into the tooth root 74 of the incisor 69 because the head end face portion 57 was formed flat.

As a result, it was extremely difficult to brush the tooth root 74 of the rear side 70 of the incisor 69 by the conventional toothbrush 50.

Fourth, as shown in FIG. 14, in the event that any orthodontic material 62 was mounted to teeth, wire 77 was disposed and fixed to the front-side lateral sides 64 of the second molar 56, first molar 60, and second premolar 61 by fixing portions 76, 76, 76.

In the event that the bristle tuft 53 of the bristle tuft unit 54 was inserted between the tooth surface and wire 77 in order to brush second molar 56, first molar 60, and second premolar 61 by the conventional toothbrush under this condition, the bristle tuft 53 interfered with the fixing portion 76 of the wire 77 and at the same time, the bristle tuft 53 was caught between the tooth surface and wire 77 and it was frequently difficult to brush the second molar 56, first molar 60, and second premolar 61.

SUMMARY OF THE INVENTION

The present invention purports to solve these conventional problems and it is therefore an object of the present invention to provide a toothbrush that can easily and surely brush lateral sides and clearances of teeth, particularly, molars and premolars, and rear surfaces of incisors.

To achieve the aforesaid object, a first aspect in accordance with the present invention provides a tooth brush having a rod-like block handle and a bristle section having a bristle tuft unit composed with a plurality of bristle tufts and extended to the end part of the block handle, wherein the bristle tuft unit is equipped with a head-end bristle tuft unit disposed in the head end section and a level difference unit provided on the block handle side rather than on the head-end bristle tuft unit, having still shorter bristle tufts and at the same time, formed throughout a plane range larger than the head-end bristle tuft unit.

In the invention according to a first aspect, the head end bristle tuft unit gets into clearances between teeth, in particular, not flat top surface of molars, gum-side lateral sides of molars, and furthermore, a clearance between lateral sides arranged oppositely with acute angles formed between adjacent molars or premolars, and the bristle tuft unit of the level difference unit fits to the top surfaces and lateral sides of molars or premolars to enable the head-end bristle tuft unit to get into clearances of the lateral sides.

In addition, even with orthodontic materials equipped, the head-end bristle tuft unit only gets into clearances between tooth front-side lateral sides and wire and the tooth front-side lateral sides are able to be brushed. Furthermore, on the rear side of incisions, too, the head-end bristle tuft unit gets into clearances between the tooth roots and gums of incisions.

In the invention according to a second aspect, the bristle tufts that form the level difference unit and are adjacent to the head-end bristle tuft unit has the shortest bristle tuft length, and at the same time, the bristle tufts are formed in such a manner that the bristle tufts gradually increase the size as they go towards the rear-end part.

Consequently, in the invention according to a second aspect, the level difference unit fits to profiles of top surfaces with irregularities formed of molars, profiles of lateral sides arranged in acute angles opposite to molars next to each other, and profiles of rear sides of incisors.

In the invention according to a third aspect, the hardness of bristles that compose the head-end bristle tuft unit is greater than that of bristles that compose the level difference unit.

Consequently, in the invention according to a third aspect, the head-end bristle tuft unit is formed to be longer than the bristle tufts of the level difference unit and at the same time, is formed in a plane range smaller than that of the level difference unit and at the same time, is harder than the tuft bristles of the level difference unit, and therefore, the toothbrush is easy to get into clearances between a plurality of molars, clearances between the orthodontic material and tooth surfaces, and furthermore, clearances between tooth roots and gums on the rear side of incisors.

In the invention according to a fourth aspect, the bristle tuft unit is composed with bristle tufts disposed in a plurality of rows along the length direction and the width direction of the block handle, rows in the length direction are disposed in a larger number of rows than that in the width direction, the head-end bristle tuft unit is composed with two rows of bristle tufts along the length direction, and at the same time, the level difference unit is composed with 7 or more rows of bristle tufts along the length direction.

In the invention according to a fifth aspect, the length of bristle tufts composing the head-end bristle tuft unit is 1 cm and at the same time, the length of bristle tufts on the third and the fourth rows that compose the level difference unit is 3 to 4 mm.

In the invention according to a sixth aspect, the length of the bristle tufts in the last row in the length direction composing the block-handle side-end portion of the level difference unit is 1 cm.

In the invention according to a seventh aspect, bristles forming the bristle tuft are formed at least one kind chosen from nylon and saturated polyester.

In a toothbrush related to the invention according to a first aspect, unlike conventional toothbrushes, the head-end bristle tuft unit gets into clearances between teeth, in particular, not flat top surface of molars, gum-side lateral sides of molars, and furthermore, a clearance between lateral sides arranged oppositely with acute angles formed between adjacent molars or premolars and the lateral sides of molars are able to be easily, quickly, and surely brushed.

In addition, on the rear sides of incisors, too, the head-end bristle tuft unit is easy to get into clearances between tooth roots and gums of incisors and the tooth roots of incisors are able to be easily and surely brushed.

In addition, even with orthodontic materials equipped, unlike conventional toothbrushes, the head-end bristle tuft unit only gets into clearances between tooth front-side lateral sides and wire, and the tooth front-side lateral sides are able to be easily, quickly, and surely brushed.

In the invention according to a second aspect, the bristle tufts that form the level difference unit and are adjacent to the head-end bristle tuft unit has the shortest bristle tuft length, and at the same time, the bristle tufts are formed in such a manner that the bristle tufts gradually increase the size as they go towards the rear-end part, and, therefore, the level difference unit fits to profiles of top surfaces with irregularities formed of molars and premolars, and profiles of lateral sides arranged in acute angles opposite to molars and premolars next to each other, and enables easy and reliable brushing.

Furthermore, when the rear sides of incisors are brushed, by using the toothbrush in the longitudinal direction, the head-end bristle tuft unit is able to be inserted between tooth roots of incisors and raised portions of gums and at the same time, the level difference unit is brought to correspond to thick wall parts of incisors and is able to be brought into contact with the rear sides of incisors while complying to the profiles of rear sides as a whole, and the rear sides of incisors are able to be easily and surely brushed.

In the invention according to a third aspect, the head-end bristle tuft unit is formed to be longer than the bristle tufts of the level difference unit and at the same time, is formed in a plane range smaller than that of the level difference unit and at the same time, is harder than the tuft bristles of the level difference unit, and therefore, the toothbrush is easy to get into clearances between a plurality of molars and premolars, clearances between the orthodontic material and tooth surfaces, and furthermore, clearances between tooth roots and gums on the rear side of incisors, and the toothbrush is able to still more easily and surely brush molars and premolars with orthodontic materials equipped and tooth roots on the rear sides of incisors.

In the invention according to a fourth aspect, the bristle tuft unit is composed with bristle tufts disposed in a plurality of rows along the length direction and the width direction of the block handle, rows in the length direction are disposed in a larger number of rows than that in the width direction, the head-end bristle tuft unit is composed with two rows of bristle tufts along the length direction, and at the same time, the level difference unit is composed with 7 or more rows of bristle tufts along the length direction, and therefore, the toothbrush maintains the overall profile same as that of conventional toothbrushes, and sense of discomfort at the time of use is able to be eliminated.

In the invention according to a fifth aspect, the length of bristle tufts composing the head-end bristle tuft unit is 1 cm and at the same time, the length of bristle tufts on the third and the fourth rows that compose the level difference unit is 3 to 4 mm, and therefore, the configuration of bristle tuft unit is same as that of conventional toothbrushes, and users are able to use the toothbrush in the same manner as conventional toothbrushes without sense of discomfort in use.

In the invention according to a sixth aspect, the length of the bristle tufts in the last row in the length direction composing the block-handle side-end portion of the level difference unit is 1 cm, and therefore, is identical to the length of bristle tufts of the head-end bristle tuft unit, and users are able to brush molars as if the toothbrush wraps around the top surfaces or lateral sides of molars by the level difference unit, enabling molars to be still more surely brushed.

In the invention according to an eighth aspect, bristles forming the bristle tuft are formed at least one kind chosen from nylon and saturated polyester, therefore, enabling the use of the toothbrush without giving users any sense of discomfort by the material same as that of conventional toothbrushes.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view illustrating one embodiment of a toothbrush according to the present invention;

FIG. 2 is a plan view illustrating the configuration state of bristle tufts of a bristle tuft unit of a tooth brush according to the present invention;

FIG. 3 is a side view illustrating the configuration state of bristle tufts of a bristle tuft unit of a tooth brush according to the present invention;

FIG. 4 is a side view illustrating one embodiment of a tooth brush according to the present invention in which the top of bristle tuft unit is brought into contact with top surfaces of second molars, and gum-side lateral sides of second molars are brushed;

FIG. 5 is a plan view illustrating one embodiment of a tooth brush according to the present invention in which a toothbrush related to the present invention is used laid down, and the brush is brought in contact with clearances between second molars and first molars and clearances with first molars and second premolars from the lateral side direction of teeth;

FIG. 6 is a longitudinal sectional view illustrating one embodiment of a tooth brush according to the present invention in which a toothbrush related to the present invention is used raised, and the bristle tuft unit is brought in contact with rear sides of incisors and tooth roots of incisors are brushed;

FIG. 7 is a side view illustrating one embodiment of a tooth brush according to the present invention in which premolars and molars are brushed when orthodontic materials are equipped to teeth;

FIG. 8 is a side view illustrating the conditions in which the bristle tuft unit is brought in contact with the gum-side lateral side of the second molar in order to brush the gum-side lateral side of the second molar using a conventional toothbrush;

FIG. 9 is a plan view comparing and illustrating cases in which the clearance between the second premolar and the first molar and the clearance between the first molar and the second molar by the use of a conventional toothbrush and a toothbrush related to the present invention;

FIG. 10 is a perspective view generally illustrating a conventional tooth brush;

FIG. 11 is a side view illustrating the conditions in which the top of the bristle tuft unit is brought in contact with the top of second molar to brush the gum-side lateral side of the second molar using a conventional toothbrush;

FIG. 12 illustrates cases in which a conventional toothbrush is used laid down, and the clearance between the second molar and the first molar, and the clearance between the first molar and the second premolar are brushed from the tooth lateral side direction with the bristle tuft unit of the tooth brush brought into contact;

FIG. 13 illustrates cases in which a conventional toothbrush is used raised, the bristle tuft unit is brought in contact with the rear sides of incisors (anterior teeth), and tooth roots of incisors are brushed;

FIG. 14 illustrates a case in which a conventional toothbrush is used to brush premolar and molars when an orthodontic material is equipped to teeth;

FIG. 15A illustrates a case in which a general toothbrush with constant bristle tufts is used;

FIG. 15B illustrates a case in which the toothbrush in accordance with aspects of the present invention is used; and

FIG. 16 illustrates the force required to bring a conventional toothbrush in contact with the tooth as shown in FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is now explained in more detail referring to embodiments illustrated in the drawings attached.

As shown in FIG. 1, a toothbrush 10 related to the present embodiment has a rod-like block handle 11 and a bristle section 13 having a bristle tuft unit 12 composed with a plurality of bristle tufts disposed of, extended to the end part of the block handle 11 via a block head 52 and extended to the end part of the block handle 11.

The bristle tuft unit 12 has a head-end bristle tuft unit 14 disposed in a head-end part 17 and a level difference unit 15 having bristle tufts 16 c through 16 h of the shorter length positioned on the block handle 11 side rather than on the head-end bristle tuft unit 14 and at the same time formed throughout a plane range larger than the head-end bristle tuft unit 14.

The bristle tufts 16 that form the level difference unit 15 are formed in such a manner that the bristle tuft 16 c adjacent to the head-end bristle unit 14 is the shortest and the bristle tufts gradually increase the size as they go towards the bristle tufts 16 h of the rear-end part.

The bristle tuft unit 12 is composed with bristle tufts 16 disposed in a plurality of rows along the length direction and the width direction of the block handle 11, and rows in the length direction are disposed in a larger number of rows than that in the width direction.

In the present embodiment, as shown in FIG. 2, the bristle tuft unit has the head-end bristle tuft unit 14 is configured with two rows of bristle tufts 16 a and 16 b along the length direction and at the same time, the level difference unit 15 is configured with 6 rows of bristle tufts 16 c, 16 d, 16 e, 16 f, 16 g, and 16 h along the length direction and 8 rows of bristle tufts 16 in the length direction as a whole. Furthermore, the bristle tuft 16 a of the first row in the length direction only is formed in two rows in the width direction.

The diameter L of the bristle tuft 16 is 1 mm and is configured with 50 to 60 bristles, and each bristle tuft 16 is disposed at intervals L1 of 2 mm with the center 19 of each bristle tuft 16 as the standard.

As shown in FIG. 3, the length L2 of bristle tufts 16 a and 16 b configuring the head-end bristle tuft unit 14 is 1 cm and at the same time the length L3 of the 3rd row bristle tuft 16 c configuring the level difference unit 15 is 4 to 5 mm, and the length L4 of the bristle tuft 16 h on the last row in the length direction configuring the block handle side-end portion 18 of the level difference unit 15 is 1 cm.

The hardness of bristles that compose bristle tufts 16 a and 16 b of head-end bristle tuft unit 14 is designed to be greater than that of bristles of the level difference unit 15. In the present embodiment, bristles that form the bristle tuft 16 are made of nylon and provide 80° C. for heat-resistant temperature.

Now, description will be made on the action of the toothbrush 10 related to the present embodiment.

In the event that as shown in FIG. 4, the toothbrush 10 related to the present embodiment is used, the bristle tuft unit 12 is positioned, for example, in the top 20 and the gum-side lateral side 21 of the second molar 56, the level difference unit 15 comes in contact with a protruded portion 22 formed on the four-corners of the top face 20 of the second molar 56, the head-end bristle tuft unit 14 goes into the clearance 24 between the gum 23 and the gum-side lateral side 21, and the toothbrush is able to easily brush the top surface 20 and the gum-side lateral side 21 of the second molar 56.

In such event, as described above, the hardness of bristles configuring bristle tufts 16 a and 16 b of the head-end bristle tuft unit 14 is formed to be greater than the hardness of bristles of the level difference unit 15, and therefore, the head-end bristle tuft unit 14 can easily go into the clearance 24.

In addition, as shown in FIG. 5, in the event that the toothbrush 10 related to the present embodiment is used to brush lateral sides of the second molar 56, first molar 60 and second premolar 61, the toothbrush 10 is laid down and inserted into an oral cavity 26 and the bristle tuft unit 12 is brought in contact with, for example, the lateral side 25 of first molar 60, the level difference unit 15 fits to the side protruded portion 27 a of the first molar 60 and the head-end bristle tuft unit 14 goes into the clearance 28 a between the first molar 60 and the second molar 61.

Consequently, the toothbrush is able to easily and surely brush the lateral side 25 of the first molar 60 and the inside of the clearance 28 a between the first molar 60 and the second molar 61.

Similarly, when the lateral sides 25 of the first molar 60 and the second premolar are brushed, the level difference unit 15 fits to the side protruded portion 27 b of second premolar 61, and the head-end bristle tuft unit 14 enters the inside of the clearance 28 b between the first molar 60 and the second premolar 61.

As a result, the lateral side 25 of the second premolar 61 and the inside of the clearance 28 a between the first molar 60 and the second premolar 61 can be easily and surely brushed.

In such event, as described above, the hardness of bristles configuring bristle tufts 16 a and 16 b of the head-end bristle tuft unit 14 is formed to be greater than the hardness of bristles of the level difference unit 15, and therefore the head-end bristle tuft unit 14 is able to easily go into the inside of clearances 28 a and 28 b.

In addition, as shown in FIG. 6, when the rear side 29 of incisor 69 is brushed using the toothbrush 10 related to the embodiment, the toothbrush 10 is set lengthwise and inserted into the oral cavity 26, and the bristle tuft unit 12 is applied to the rear side of incisor 69.

In such event, the level difference unit 15 fits to a thick wall part 71 of incisor 69, and the head-end bristle tuft unit 14 goes into a clearance 30 between a raised portion 73 and the thick wall part 71 of gum 23. As a result, the rear side 29 of incisor 69 and the inside of clearance 30 between the thick wall part 71 of incisor 69 and raised portion 73 of gum 23 can be easily and surely brushed.

In such event, as described above, the hardness of bristles configuring bristle tufts 16 a and 16 b of the head-end bristle tuft unit 14 is formed to be greater than the hardness of bristles of level difference unit 15, and therefore, the head-end bristle tuft unit 14 is able to easily go into the inside of the clearance 30.

Furthermore, as shown in FIG. 7, in the event that lateral sides 31 of second molar 56, first molar 60, and second premolar 61 are brushed with an orthodontic material 62 equipped to teeth, the head-end bristle tuft unit 14 is inserted from below into a clearance between lateral sides 31 of second molar 56, first molar 60, or second premolar and wire 77 in such a manner that the level difference unit 15 corresponds to the fixing portion 76 of wire 77 configuring the orthodontic material 62.

As a result, the head-end bristle tuft unit 14 gets into a clearance between lateral sides 31 of second molar 56, first molar 60 or second premolar 61 and wire 77, and teeth lateral sides 31 are able to be brushed.

In such event, in the present embodiment, the length of the bristle tuft 16 configuring the level difference unit 15 is the longest at bristle tufts 16a and 16b of the head-end bristle tuft unit 14 and at the same time, in the level difference unit 15, the bristle tuft 16 c is the shortest and the bristle tufts are formed in such a manner that the bristle tufts gradually increase the size as they go towards the rear-end part, and the length L4 of bristle tuft 16 h of the last row in the length direction of the level difference unit 15 is formed to be identical to the length L2 of bristles of the head-end bristle bundle unit 14, and therefore, the level difference unit 15 is positioned along the profile of teeth lateral sides 31, enabling the toothbrush to properly brush the lateral sides 31 of teeth to which wire 77 is not disposed.

In addition, as described above, the hardness of bristles configuring bristle tufts 16 a and 16 b of the head-end bristle tuft unit 14 is formed to be greater than that of bristles of the level difference unit 15, and therefore, the head-end bristle tuft unit 14 is able to easily go into a clearance between lateral sides 31 of second molar 56, first molar 60 or second premolar 61 and wire 77.

EXAMPLE 1

As described below, comparison experiments were performed on a toothbrush 10 related to the embodiment and a conventional toothbrush 50 with the head-end face portion of the bristle tuft unit of the block head formed flat.

1) Insertion Angle of the Block Head into the Oral Cavity

Investigation was made on the angle made by the toothbrush block handle and the median line between central incisors when an interdental portion of the upper right second molar and the upper right first molar was cleaned. In Table 1, the upper column indicates the angle made by a conventional toothbrush and the lower column by a toothbrush related to the present invention.

In this case, it is assumed that the smaller the above-mentioned angle made, the more available is the brushing free of unnecessary force to arms, hands, etc.

TABLE 1 General toothbrush with bristle tufts of constant around 50 degrees length Toothbrush according to the present invention around 25 degrees

As shown in Table 1, the toothbrush related to the invention as claimed in the application concerned is able to be inserted in the oral cavity under the condition closer to parallel to the median line and brought to reach the target portion, and is therefore assumed to provide higher operability as a toothbrush. Consequently, higher operability will result in improved cleaning efficacy.

The toothbrush related to the present invention provides an angle half as much as that of conventional toothbrushes, and the toothbrush related to the present invention enables brushing under the condition overwhelmingly free of burden to the arm and the hand.

2) Accessibility of a Toothbrush to the Interdental Portion

Maxillary oral cavity models were created using hard white gypsum. Red Coat was applied to two rows at the head end of a conventional toothbrush with bristle tufts of same length and to two rows at the head end of a toothbrush related to the present invention, and teeth were brushed for 20 seconds with the insertion angle kept identical (30 degrees to the dentition). The Red Coat (dental plaque stain) adhering to gypsum was compared and the cleaning efficacy was investigated.

When the interdental portion is attempted to be selectively brushed by a conventional toothbrush with same bristle tuft length, the unclean areas are left on the lateral side of the second premolar as shown in FIG. 15A (area 80).

In addition, because an effort is made to insert bristles into the interdental portion, the brush pressure increases (deposit of pigment is stronger than that in FIG. 15B) and nociceptive stimulus to gums increases. Furthermore, the poor brush operability causes the brush to come in contact with the area exceeding the range of target portion.

From the viewpoint of cleaning a large area at once, the conventional toothbrush with the same bristle tuft length is advantageous, but from the viewpoint of cleaning target portions (such as cleaning of teeth equipped with orthodontic materials, or pinpoint cleaning of interdental tooth necks), the toothbrush related to the present invention has a far bigger advantage.

3) Force Required to Clean Lateral Sides of Molars

As shown in FIG. 8, when a conventional toothbrush 50 with the same bristle tuft length is used, for example, in order to bring the bristle tuft unit 58 in contact with the top surface of the second molar 56 and allow the toothbrush 50 to reach the lateral sides 58 of the second molar 56, the toothbrush must be brought in contact with the tooth in such a manner that the center portion 65 (the rear portion depending on how the toothbrush is brought in contact with) is bent. The force required in such event was measured (FIG. 16).

On the other hand, in the toothbrush 10 related to the present invention, this kind of force to reach the tooth is not required. Incidentally, the toothbrush weight is not taken into account.

4) Cleaning of the Interdental Portion

As shown in FIG. 9, Paragraph 3) above applies in the same way when the interdental portion, for example, the spaces between the second premolar 61, first molar 60, and second molar 56 are cleaned from the lateral side direction.

As shown in FIG. 9, in the bristle tuft unit 54 of the conventional toothbrush 50, the head end portion 74 of the bristle tuft unit 54 is unable to be inserted into the interdental portion 78 unless the portion shown by symbol A is bent.

That is, in order to allow the bristle tuft unit 54 to reach the interdental portion 78, the target portion, as shown in FIG. 9, force must be partially applied to the bristle tuft unit 54 and part of bristle tufts 53 must be attempted to be bent.

As a result, in the conventional toothbrush 50, to clean the interdental portion 78, extra force is required and it is impossible to easily and surely brush teeth with an appropriate force.

On the other hand, in the tooth brush 10 related to the present invention shown in FIG. 9, by applying, for example, the level difference unit 15 to the side protruded portion 27 of the first molar 60, the head-end bristle tuft unit 14 is able to be easily inserted into the interdental portion 78 between the second molar 56 and the first molar 60, which has become clear by experimental results.

Incidentally, the bristle tuft unit width size and arrangement size, arrangement condition of the bristle tuft unit, and bristle tuft material in the present embodiment are not restricted by the present embodiment.

The present invention is able to be extensively applied to a toothbrush that is easy to brush molars, premolars, and incisors, and therefore, has industrial applicability. 

What is claimed is:
 1. A tooth brush, comprising: a rod-like block handle and a bristle section having a bristle tuft unit composed with a plurality of bristle tufts and extended to the end part of the block handle, wherein the bristle tuft unit is equipped with a head-end bristle tuft unit disposed in the head end section and a level difference unit provided on the block handle side rather than on the head-end bristle tuft unit, having still shorter bristle tufts and at the same time, formed throughout a plane range larger than the head-end bristle tuft unit.
 2. The toothbrush according to claim 1, wherein the bristle tufts that form the level difference unit and are adjacent to the head-end bristle tuft unit has the shortest bristle tuft length, and at the same time, the bristle tufts are formed in such a manner that the bristle tufts gradually increase the size as they go towards the rear-end part.
 3. The toothbrush according to claim 2, wherein the hardness of bristles that compose the head-end bristle tuft unit is greater than that of bristles that compose the level difference unit.
 4. The toothbrush according to claim 3, wherein the bristle tuft unit is composed with bristle tufts disposed in a plurality of rows along the length direction and the width direction of the block handle, rows in the length direction are disposed in a larger number of rows than that in the width direction, the head-end bristle tuft unit is composed with two rows of bristle tufts along the length direction, and at the same time, the level difference unit is composed with 7 or more rows of bristle tufts along the length direction.
 5. The toothbrush according to claim 4, wherein the length of bristle tufts composing the head-end bristle tuft unit is 1 cm and at the same time, the length of bristle tufts on the third and the fourth rows that compose the level difference unit is 3 to 4 mm.
 6. The toothbrush according to claim 5, wherein the length of the bristle tufts in the last row in the length direction of the level difference unit is 1 cm.
 7. The toothbrush according to claim 1, wherein the diameter of the bristle tuft is 1 mm and is composed with 50 to 60 bristles, and each bristle tuft is arranged at intervals of 2 mm with the center of each bristle tuft set as a standard.
 8. The toothbrush according to any one of claims 1 through 7, wherein bristles forming the bristle tuft are formed at least one kind chosen from nylon and saturated polyester. 